just returned from a 2 week trip in Canada. It got down to -6C but I was toasty in my 30 degree peapod with yeti underquilt and JRB Stealth top quilt. So warm infact that I had to vent the peapod down to my waist!
The setup took up half my pack, but it was a comfort to know that no matter how cold it got, I would be fine.
The only problem was that towards the end of the trip, I stank so much that I couldn't bear to seal up the peapod, the smell was awful!
The trip was centered around primitive skills rather than hiking, so the camping took place in base camps. I also tested out a 10 by 10 winter tarp made up for me by our own forum member Hitchhiking, this also added a lot to the warmth. With the doors of the tarp closed, lying in the sealed peapod with both quilts, I had quite the little microclimate going on